In afternoon trade, the S&P/ASX 200 Index (ASX: XJO) is on course to record a small decline. At the time of writing, the benchmark index is down 0.1% to 7,923.1 points.

Four ASX shares that are falling more than most today are listed below. Here's why they are dropping:

Helia Group Ltd (ASX: HLI)

The Helia Group share price is down 27% to $3.55. Investors have been selling this lenders mortgage insurance (LMI) provider's shares after it conceded that it is likely to have lost its major contract with Commonwealth Bank of Australia (ASX: CBA). The company notes that the LMI business underwritten under this contract represented approximately 44% of gross written premium (GWP) in FY 2024. CEO and managing director, Ms Pauline Blight-Johnston, said: "Together, CBA and Helia have helped hundreds of thousands of Australians to buy homes over the last 50 years. Given our longstanding and successful relationship with CBA, we are disappointed in this development. We would have welcomed the opportunity to continue our partnership."

James Hardie Industries plc (ASX: JHX)

The James Hardie Industries share price is down 12% to $41.00. This morning, this building materials giant announced an agreement to acquire The AZEK Company Inc. (NYSE: AZEK) in a deal valued at US$8.75 billion (A$14 billion), including AZEK's net debt. Management has spoken very positively about the transaction, but it seems that the market doesn't agree. CEO Aaron Erter said: "We are uniting two highly complementary companies with large material conversion opportunities and shared cultures centered around providing winning solutions to our customers and contractors. Together, we will be well positioned to drive sustained above market growth as a leader across attractive categories for the exterior of the home."

New Hope Corporation Ltd (ASX: NHC)

The New Hope share price is down 6% to $3.86. This has been driven by the coal miner's shares going ex-dividend this morning. Last week, New Hope released its half year results and declared a fully franked 19 cents per share interim dividend. This equates to a sizeable 4.1% dividend yield based on its last close price. Eligible shareholders can now look forward to receiving this next month on 9 April.

Synlait Milk Ltd (ASX: SM1)

The Synlait Milk share price is down 9% to 83 cents. This follows the release of the dairy processor's half year results. Synlait posted EBITDA of NZ$63.1 million for the half, just above its the guidance range. It also reported a net profit after tax of NZ$4.8 million. Looking ahead, management warned that "financial progress made in the second half of FY25 will be slower than the first half."